Food storage systems can allow food to be preserved under better conditions than if the food were stored without such systems. One way to improve the storage of food is to keep it in a container under vacuum. Such systems have been shown to produce very good results in protecting food from certain microorganisms, pests, mold and fungus growth. Furthermore, they help to prevent the food from oxidizing, maintaining the moisture level and aroma of the food.
Lids for storage containers can include a venting or aerating valve for the equalization of pressure during heating in a microwave oven.
EP 0 633 196 A2 describes such a lid. The objective of EP 0 633 196 A2 is to prevent the build-up of overpressure in the interiors of food storage containers that are heated in a microwave oven. The build-up of overpressure tends to occur when there are aqueous liquids in a container interior. The liquids can evaporate during heating, thereby building up an overpressure in the interior of the container. This is a disadvantage particularly when opening the container lid because it can cause sauces or other food items to spurt out suddenly when the lid is opened. EP 0 633 196 A2 proposes a venting valve in the lid of the food storage container. The venting valve is to be opened before the container is placed in the microwave oven. Water vapor developing during the heating operation can then escape unhindered through the valve without a corresponding build-up of vapor pressure in the interior of the sealed container.
The objective of EP 0 820 939 A1 also is the prevention of the build-up of overpressure in the interiors of food storage containers that are heated in a microwave oven. In other words, the objective is to provide food storage containers with venting capability, in order to be able to safely heat in a microwave oven the food stored inside of the containers, with the container lid closed. Unlike EP 0 633 196 A2, a valve mechanism is described which can be opened by way of a joint like a rocker. Hence all that is required is to press in the rocker lever for the valve to open with ease.
WO 88/00560 describes an opening mechanism for a plastic beverage can. By opening a venting valve, the pressure can be equalized, thereby making it easier to subsequently open and pull off the entire lid. The lids in WO 88/00560 invariably are plastic lids, because an objective is to avoid the use of metal lids. In particular, the equalization of overpressure in the interior of the container resulting from carbonated beverages, for example, plays a role in this case.
Further, U.S. Pat. No. 3,737,066 discloses a container devised preferably for the storage of liquids. The side walls of the container are made of a coated carton material, and the base and lid elements of the container are comprised of plastic plates connected with the carton walls in a liquid-tight relationship. The upper plastic lid has a reclosable opening mechanism which is also made of plastic and is positively engaged with the lid by holding pins. No provision is made for venting prior to opening the container lid or for a device for pressure equalization.
CH 304 374 discloses a closure lid for an aluminum sterilizing container. The lid has an essentially circular-ring-shaped configuration, and it is mounted on a cylindrical aluminum container. A rubber seal is placed between the edge of the lid and the upper brim of the container. Provided in the middle of the container lid is an additional opening which is covered by a rubber cap. The rubber cap provides a visual check, indicating whether there is a vacuum inside the container. As long as the pressure inside the container is adequately below atmospheric pressure, the rubber cap bulges inward a corresponding amount. This bulge diminishes continually as the vacuum decreases. Hence it is difficult for the observer to decide whether the pressure level inside the container is adequate for ensuring the freshness of the food inside the container.
U.S. Pat. No. 5,195,427 and WO 97/17259 both describe vacuum pumps for evacuating food storage containers. In each specification, conically extending suction tips are inserted in corresponding valve openings in storage container lid.
EP 0 234 607 B1 describes a bottle closure which also serves as a vent valve. A cylindrical vacuum pump is connected thereto, such that it fully encompasses the projecting cylindrical shank of the bottle closure.
EP 0 644 128 A1 describes a sealable container adapted to be evacuated by a vacuum pump. A one-way valve is received in a cylindrical recess in the container lid, and the suction opening of a vacuum pump is inserted therein.
In DE-74 09 380 U, a food storage container includes a filling opening which is closable by a lid. At its center, the lid has a vent opening which is closable by a valve element. The valve element has an opening lug which allows the valve element to be lifted off the vent opening, thus enabling the vacuum existing inside the storage container to be reduced. After cooking, a vacuum can be obtained in the storage container by allowing the food to cool with the valve closed.
Furthermore, in DE-28 21 852 A1, a food storage container is closable air-tight by a lid equipped with a valve. The valve is arranged at the center of the lid and is surrounded by an annular connecting device on which a vacuum pump for venting the food space of the storage container is mountable. To open the storage container, the valve disk has to be lifted off the sealing edge formed on the lid, which can be done by the user reaching with a knife or some other pointed object under the valve disk and pressing it upward.
To generate a vacuum in a food storage container, a device can be used to draw air out of the container. A wide variety of pumps for performing this function are known from the art. As a rule the pumps intended for household use are based on piston pumps or ventilators.
U.S. Pat. No. 5,195,427 discloses a prior-art electrically powered handheld vacuum pump for use in the household. The handheld device is constructed from a multiplicity of single parts for use solely as a vacuum pump. In particular, the shaft's rotary motion is elaborately converted into an oscillating motion. A suitable reduction gear drives the piston pump. The system is intended for the evacuation of food storage containers. With this device, it is possible to easily obtain a suitable pressure ratio for storing food in a vacuum container.
DE 195 04 638 A1 discloses an immersion blender for mixing or comminuting food. The blender includes a blade which rotates in a bell-shaped recess, thereby generating a vacuum. The vacuum that accumulates in the bell serves to improve and intensify the mixing of food.
In 299 20 316 U1, a device generates a vacuum in a container by using a vacuum-cleaner as a vacuum generator. An adapter piece in the form of an attachment to a vacuum-cleaner is mountable on a valve arranged on the container lid.